Fusion carbide of refractory metal cementing

ABSTRACT

Fusion carbide of a refractory metal cementing is disclosed, which includes at least four strengthening compound phases and at least one refractory metal cementing phase. The strengthening compound phases and the refractory metal cementing phase are combined by a fusion method, for manufacturing the refractory metal cementing fusion carbide. By using the fusion method, the problems of low density and high cost in the conventional sintering method for combining the strengthening phase and the cementing phase can be solved, and composite material with high hardness, high melting point, and high toughness can be manufactured. Moreover, comparing with the conventional sintered cermet composite material, the refractory metal cementing fusion carbide has the advantages including rapid and convenient manufacturing, with desired density, and hardness and toughness.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to fusion carbide of a refractory metal cementing; and in particular, to combining the multi-component compounds strengthening phase and the fewer-component refractory metal cementing phase by using a fusion method, for manufacturing a composite structure which has a dendrite and an inter-dendrite.

2. Description of Related Art

The cemented carbide is a composite material which is formed by combining WC and Co. In early 19^(th) century, the French, Henri Moissan, is the first one who composed and made tungsten carbide (WC). Originally, the tungsten carbide was supposed to be used for replacing diamonds because of its high hardness, but due to its fragility and the presence of holes, the tungsten carbide is not an ideal option in engineering applications. In 1923, Schroter and Baumhauer recognized that after the tungsten carbide is sintered and combined with cobalt and nickel, it can keep the hardness of the ceramic materials and the toughness of the metal. For mold industry, such discovery is influential and is widely applied to cutting tools, mineral excavation, and the components of military weapons. The required quantity of usage grows rapidly year after year. The amount of usage of the discovered material was 10 tons in 1930. In 2008, it reached 50,000 tons, which grows 5,000 times in 78 years. Around 60% of raw material tungsten is used for manufacturing the cemented carbide.

The cementing carbide is made of two parts, one of which is strengthening phase and the other is cementing phase. The aforementioned tungsten carbide (WC) serves as the part of strengthening phase, which is associated with high melting point, high toughness, and good anti-wearing properties. On the other hand, the cobalt serves as a cementing phase, which corresponds to good electrical and heat conduction of metals, and ensures the composite materials is not fragile.

Most of the recent investigation takes additional strengthening phases, such as TiC and TaC, and additional cementing phases, such as Mo, Ni, and Fe. The composed materials are called cermet composite materials. The main conventional manufacturing processes of the hard metals including cermet composite materials are sintering methods. The micro-structure of the sintering method mainly includes micron-scale carbide (such as WC) particles and the cementing metal phase (such as Co), which has non-zero porosity and relatively inferior toughness. Although the relatively higher hardness and strength can be achieved when the micron-scale WC particle-cementing Co is sintered at 1,600 degrees Celsius, the 3,500 degrees Celsius in connection with the fusion method can easily cause the material to have large particle in micro-structure, low hardness, and low strength. Therefore, the current-existed cemented carbide composite materials are all manufactured by sintering.

Although the products made by the conventional sintering processes can preserve relatively higher low-temperature hardness and higher low-temperature strength, the sintering processes are delicate and complicated, and the products made thereby have relatively inferior toughness. In addition, because using high-temperature refractory cementing metal can raise melting point, high-temperature hardness and high-temperature strength of the products thereof can also be raised. However, if the cementing metal uses high-temperature refractory metals for the sintering processes, the sintering of the high-temperature refractory metal would be challenging because the sintering processes renders difficult the refractory metal to stay in liquid state.

Therefore, the present disclosure uses the fusion method for performing melting processes to the compound by using the high-temperature refractory metal as the cementing metal. In addition to preserving high melting point, the composite materials manufactured according to the present disclosure would be associated with the properties of corrosion resistance, high melting point, high hardness, high strength, and high toughness. Moreover, the fusion method is much simpler and faster than the sintering method, and the micro-structure of the product manufactured by the fusion method is the typical dendrite and inter-dendrite structure which has zero porosity and good toughness.

SUMMARY OF THE INVENTION

The present disclosure shows fusion carbide of a refractory metal cementing, and is able to combine the multi-component-compounds strengthening phase and few-component refractory metal cementing phase by fusion method, for manufacturing a composite structure which has dendrite and inter-dendrite.

Fusion carbide of a refractory metal cementing is disclosed, and includes at least four kinds of compounds strengthening phase and at least one refractory metal cementing phase. The compounds strengthening phase and the refractory metal cementing phase are combined by a fusion method, for manufacturing a refractory metal cementing fusion carbide.

Specifically, the strengthening compound phase is chosen from the group consisting of TiC, ZrC, NbC, VC, TaC, WC, HfC, TiN, and ZrN compounds. Four or more than four compounds are selected from the aforementioned group for combining with the refractory metal cementing phase by the fusion method.

Specifically, the refractory metal cementing phase is chosen from the group consisting of Mo, W, Nb, Hf, Ta, and Re. At least one refractory metal cementing phase shown in the aforementioned group is selected and combined with the compounds strengthening phase.

Specifically, the fusion method is a vacuum arc melting method operating at the temperature which exceeds 3,500 degrees Celsius, for making the manufactured refractory metal cementing fusion carbide to have a composite structure including a dendrite and an inter-dendrite.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings included herein provide further understanding of the present disclosure. A brief introduction of the drawings is as follows:

FIG. 1 shows a flow chart for manufacturing a fusion carbide of a refractory metal cementing according to the present disclosure;

FIG. 2 shows a schematic diagram of a cermet code and a cermet composition of a fusion carbide of a refractory metal cementing according to the present disclosure;

FIG. 3 shows a schematic diagram of a cermet ingredient of a fusion carbide of a refractory metal cementing according to the present disclosure;

FIG. 4 shows a schematic diagram of a cermet ingredient weight ratio of a fusion carbide of a refractory metal cementing according to the present disclosure;

FIG. 5 shows a schematic diagram of a cermet ingredient volume ratio and a total density of a fusion carbide of a refractory metal cementing according to the present disclosure;

FIG. 6A shows a 200 times enlarging diagram of a BEI image of a C1M1 cermet of a fusion carbide of a refractory metal cementing according to the present disclosure;

FIG. 6B shows a 1,000 times enlarging diagram of a BEI image of a C1M1 cermet of a fusion carbide of a refractory metal cementing according to the present disclosure;

FIG. 7A shows a 200 times enlarging diagram of a BEI image of a C4M1 cermet of a fusion carbide of a refractory metal cementing according to the present disclosure;

FIG. 7B shows a 1,000 times enlarging diagram of a BEI image of a C4M1 cermet of a fusion carbide of a refractory metal cementing according to the present disclosure;

FIG. 7C shows a 3,000 times enlarging diagram of a BEI image of a C4M1 cermet of a fusion carbide of a refractory metal cementing according to the present disclosure;

FIG. 8 shows a schematic diagram of the total hardness, toughness, and phase hardness values of C1M1 to C7M1 of a fusion carbide of a refractory metal cementing according to the present disclosure;

FIG. 9A shows a schematic diagram of the total hardness, phase hardness values, and the wear resistance of C1M1 to C7M1 of a fusion carbide of a refractory metal cementing according to the present disclosure;

FIG. 9B shows a schematic diagram of a trend between a MC phase hardness value and the wear resistance of C1M1 to C7M1 of a fusion carbide of a refractory metal cementing according to the present disclosure;

FIG. 10 shows a schematic diagram of a hardness performance of C1M1 to C7M1 at the temperature ranging from room temperature to 1273 K of a fusion carbide of a refractory metal cementing according to the present disclosure;

FIG. 11 shows a schematic diagram of a cermet code and a cermet composition of the variables of a strengthening phase carbide and a cementing phase metal of C6M1 system of a fusion carbide of a refractory metal cementing according to the present disclosure; and

FIG. 12 shows a schematic diagram of a cermet ingredient of the variables of strengthening phase carbide and a cementing phase metal of C6M1 system of a fusion carbide of a refractory metal cementing according to the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

For further understanding of the present disclosure, reference is made to the following detailed description illustrating the embodiments and examples of the present disclosure. The description is only for illustrating the present disclosure, not for limiting the scope of the claim.

The present disclosure uses a fusion method for combining at least four strengthening compounds with at least one cementing refractory metal, for manufacturing a refractory metal cementing fusion carbide. The following embodiment takes TiC (which has melting point over 3,000 degrees Celsius and over 3,000 HV in hardness) and the refractory metal Mo for manufacturing the cermet materials with different percentages of TiC and Mo. Moreover, the embodiment also multiply-adds interstitial type of VI, V, VI B group carbides, such as ZrC, HfC, VC, NbC, TaC, and WC, into the materials, for manufacturing a refractory metal cementing fusion carbide.

As shown in FIG. 1, the present embodiment uses a vacuum arc melting furnace for refining alloys. The strengthening phase compound powders and the raw metal materials are weighted about 50 grams in total, and are disposed into the water-cooling copper mold (101). After the upper furnace lid is closed and the furnace is vacuumed to 2.4×10⁻² torr, the argon gases are filled in until the pressure is about 8.0 torr, at which point the furnace is vacuumed again. After the above purging processes are executed three times, the fusion processes could be considered completed (102). The fusion current is 550 amperes. After the fusion processes concludes and the materials are completely cooled down, the alloy piece is then flipped and fused again. The flipping and fusing processes are performed over four times, for ensuring that all of the cermet elements are well mixed in the test pieces. The ingots are taken out after being completely cooled down, and the ingots are called as-cast state testing piece (103).

The present embodiment analyzes 7 sets of cermets, and the cermet codes and the compositions of the 7 sets of cermets are shown in FIG. 2, the cermet ingredients (at %) are respectively shown in FIG. 3, the cermet ingredient weight (wt %) is shown in FIG. 4, and the cermet ingredient volume (vol %) and the total density (g/cc) are shown in FIG. 5. After the ingredients of the 7 sets of cermets are arranged, the alloys are fused and manufactured by the vacuum arc fusion furnace, and then the manufactured as-cast state testing pieces is analyzed by the following processes:

(1) preliminarily analyzing the ingredients and the microstructures of the surfaces thereof by a scanning electronic microscope;

(2) measuring the x-ray diffraction thereof by an XRD;

(3) measuring the total hardness of the cermet by using a Vickers hardness machine;

(4) performing the wearing test of a dry grinding under the condition with no lubrication;

(5) measuring the high-temperature hardness by using a high-temperature hardness meter machine; and

(6) cutting the material into the shape of the rhombus turning tool and polishing the material, for performing the cutting test.

The analyses of the micro-structure of the 7 sets of the cermet are shown in the following descriptions.

(1) The C1M1 to C3M1 mainly have two structures associated with diffraction peaks (an MC type carbide (Metal:Carbide=1:1) of the FCC structure and a solid solution of Mo of BCC structure), and the C4M1 mainly has three structures associated with diffraction peaks (an MC type carbide of the FCC structure, a solid solution of Mo of BCC structure, and an M₂C type carbide (Metal:Carbide=2:1) of Hexagonal structure.

(2) As shown in FIGS. 6A and 6B which include the 200 times and 1,000 times BEI images of the C1M1 cermets, respectively. In the C1M1 cermet, the black phase is a primary crystal which solid-solutionizes some Mo, and the layered eutectic structure is formed by combining the eutectic crystal TiC and the solid solution of Mo. The figures show the typical dendrite and inter-dendrite structure, wherein the black phase is the dendrite structure and the white phase is the inter-dendrite structure.

All parts of the C1M1 to C7M1 cermets show the dendrite and inter-dendrite structure. As shown in FIGS. 7A to 7C which respectively include the 200 times, 1,000 times, and 3,000 times of magnification of BEI images of the C4M1 cermet, it could be seen that the microstructures therein have great differences from the microstructures of the C1M1, C2M1, and C3M1. By x-ray diffraction analysis, the BEI metal phase structure in this embodiment mainly has four phases: the black phase, the white phase, the eutectic structure, and the greatest feature “gray phase,” as shown in the figures. The black phase is similar to the above mentioned three systems, all of which are either a primary crystal MC type carbide ((Ti+Zr+Nb+V):Carbon=1:1), or (Ti, Zr, Nb, V)C dissolved with few solid solution of Mo. The layered eutectic structure is formed by combining the eutectic MC type carbide and the solid solution mainly containing Mo. In addition, in this system, the amount of the cermet layered eutectic structure is obviously decreasing, and more white phase is generated, wherein the white phase is the solid solution mainly including Mo. The gray phase is inferred to be the M₂C type carbide ((Ti+Zr+Nb+V+Mo):Carbon=2:1), and is converted from parts of the inter-dendrite white phase. Different from the MC type carbide, the M₂C type carbide can dissolve more Mo (about 46 at %), compared to the MC type carbide that dissolving about 17 at % of Mo. The hardness of this phase is between the hardness of the MC type carbide and the white phase of the solid solution of metal Mo. However, because this phase is observed in the inter-dendrite metal cementing phase, it is considered that the total hardness is greatly raised.

(4) The C4M1 to C7M1 cermets have the similar microstructure as the C4M1 cermet. Therefore, with the multi-component adding (C4M1 to C7M1), the hardness of the Mo based carbide cermet system raises obviously. When VC is added, the M₂C type carbide could result and the cermet has the similar inter-dendrite structure as the solid solution of the cementing phase Mo.

The measuring results of total hardness of the 7 sets of cermets are shown in FIG. 8, wherein the hardness represents the total hardness, the K_(w) represents the toughness, and the HV represent the phase hardness. The increase in hardness from C1M1 to C3M1 is not obvious. Specifically, the average phase hardness of C4M1 to C7M1 is about 1700 HV. Although the increase in hardness value is not as much as the strengthening phase MC carbide, it is still more than that of the cementing phase Mo. Moreover, the C6M1 system reaches the highest 1203 HV in hardness.

The results of the wearing tests toward the 7 sets cermets are shown in FIG. 9A. As shown in the figure, the wear resistance has positive correlation with the phase hardness of the MC carbide. As shown in FIG. 9B, the curve is separated into three linear trend stages:

(1) In the first stage, there is a phenomenon that the resistance between C2M1 and C1M1, which is cause by the decreasing of the phase hardness of the MC carbide (the MC carbide of the C2M1 is formed by the precipitation of the ZrC having relatively higher melting point and softer hardness).

(2) In the second stage, the wearing resistance between C3M1 to C6M1 is gradually increasing. In addition to the reason that the phase hardness of the MC carbide is raised by the multi-component adding, the M2C carbide being precipitated from the inter-dendrite is one of the reasons that cause this phenomenon.

(3) In the last stage, the decreasing of the wearing resistance is because the phase hardness of the MC carbide between C6M1 to C7M1 decreases, and the strong carbide to form HfC added for making the M2C carbide in the inter-dendrite is greatly reduced.

Therefore, from the C4M1 system, due to the continuously raising phase hardness of the strengthening phase MC carbide caused by the precipitation of the M₂C carbide from the inter-dendrite, the partial fracture is caused and the density is reduced. Moreover, the scratching of the base phase becomes less noticed, thus increasing the total wearing resistance. The wearing resistance of C6M1 reaches 31.26 m/mm³.

The results of high-temperature hardness of the 7 sets cermets are shown in FIG. 10. As shown in FIG. 10, the hardness performance trend shows that the hardness of the testing piece gradually reduces during the increasing of the temperature in the C1M1 to C7M1 systems (the temperature raises 200 degrees Celsius from the room temperature to 1,000 degrees Celsius). C2M1 is subjected to least hardness decreasing while C6M1 is associated with the largest decline in hardness. The C7M1 may be associated with the greatest hardness at 1,000 degrees Celsius, which is about 850 HV. The C6M1 may be with the greatest hardness in the temperature window from the room temperature to 600 degrees Celsius, which is about 800 HV. C6M1 may still be with the second place hardness at 1,000 degrees Celsius, which is also about 800 HV compared with its counterparts in the embodiment of the present disclosure.

After the 7 sets of cermets are cut into the shape of rhombus turning tool and polished for the cutting test, the C6M1 has relatively good cutting performance among all of the test pieces.

On the basis of the above, the C6M1 has the greatest hardness and wearing resistance performances, and good high-temperature hardness and toughness among the Mo based cermet carbide strengthening phase multi-component adding systems. Thus, taking the C6M1 cermet system as basis, the variables of the strengthening phase carbide and the cementing phase metal Mo are arranged in this system. The variables is that choosing the hardest carbides in the IV, V, VI B group carbide and increasing the arranged ratios thereof. The arranged cermet codes and compositions of C6M1 are shown in FIG. 11, and the arranged cermet ingredients (at %) of the C6M1 are shown in FIG. 12. The analyses of the above mentioned arrangements are shown in the following descriptions.

(1) The C6M1Ti2, C6M1V2, and C6M1W2 mean that the ingredient ratios of TiC, VC, and WC are doubled respectively. After analyses, the hardness and toughness of the C6M1W2 are obviously increased comparing with C6M1 (although the hardness of C6M1V2 is increased also, the toughness performance thereof is not as desired as C6M1W2).

(2) The C6M1W2, C6M1W3, and C6M1W4 mean that the ingredient ratios of WC are doubled, tripled, and quadrupled respectively. After analyses, the hardness and toughness of C6M1W4 are obviously reduced comparing with C6M1W3. Moreover, as WC increases, the Mo of the inter-dendrite is decreased and replaced by M₂C, thus the toughness thereof is reduced.

(3) The C6M1aW3Mo55, C6M1aW3Mo45, C6M1aW3Mo40, and C6M1aW3Mo30 are the cermet codes that the ingredients of Mo in the C6M1W3 are 55, 45, 40, and 30 at %, respectively. After analysis, although the amount of Mo in C6M1W3 cermet is adjusted, the microstructure is composed of the FCC MC carbide, the Hexagonal M₂C carbide, and the BCC solid solution of Mo. As the amount of Mo decreases, the total performance includes the similar hardness as ceramic materials despite being more fragile.

(4) The (WC)₃ may be adjusted into (WC)₂₅ and (WC)₃₅. For description purpose, as the (WC)₃ is abbreviated into C6M1W3, the (WC)₂₅ and (WC)_(3.5) can also be abbreviated into C6M1W2.5 and C6M1W3.5. The Mo contained in C6M1W2.5 may be adjusted into 45 and 55 at %, which could be represented by C6M1′W2.5Mo45 and C6M1′W2.5Mo55, respectively. After analysis, the differences between the C6M1W2.5, C6M1′W2.5Mo45 and C6M1′W2.5Mo55 cermets are that the HV of the C6M1W2.5 cermet is higher than the HV of C6M1W3 by about 40 HV, and the K_(1c) toughness of the C6M1W2.5 is at 9.15 MPa·m^(1/2).

The changes caused by the variables of the C6M1 based cermets are shown in the following descriptions.

(1) Comparing the hardness and microstructures of the C6M1 cermets of different WC amount, although the WC adding may increase the hardness of the C6M1 cermet, the optimal amount of WC adding may be 2.5 times. Excessive WC may result in eutectic structures which cause the reduction in the cermet hardness.

(2) In the wearing tests for both C6M1W2.5 and C6M1W3 as the top two examples in hardness, the broken condition and scratching mark are less significant in C6M1W2.5. The wearing resistance is up to 39.98±1.62 m/mm³ The C6M1W3, meanwhile, has the larger wearing resistance than C6M1, which is 35.59±1.43 m/mm³.

(3) Although the reduction of the amount of cementing metal Mo may increase the hardness, that increase could be at the expense of the toughness, which may be greatly decreased at the same time.

(4) In summary, by proper few-component adding of the refractory metal cementing, the hardness and toughness performances may be improved, but multi-component adding is not suitable to the refractor metal cementing.

Comparing the fusion carbide of the refractory metal cementing provided by the present disclosure with the conventional techniques, the advantages are shown as follows:

1. The present disclosure uses fusion method for combining at least four multi-component strengthening phase compounds with at least one few-component refractory metal cementing phase, for manufacturing a refractory metal cementing fusion carbide. The combination of the strengthening phase and the cementing phase is able to overcome the problems of low density and high cost in connection with the conventional techniques, and composite material with high hardness, high melting point, and high toughness can also be manufactured.

2. The refractory metal cementing fusion carbide manufactured according to the present disclosure has relatively larger dendrite and inter-dendrite structures, which are opposite to the sub-microstructure scale arising out of the sintering processes. However, the total processes shown in the present disclosure are faster and much convenient than the conventional processes, and the composite material manufactured according to the present disclosure has been consistent in better performance in hardness and toughness, compared with the conventional sintering composite materials.

Some modifications of these examples, as well as other possibilities will, on reading or having read this description, or having comprehended these examples, will occur to those skilled in the art. Such modifications and variations are comprehended within this disclosure as described here and claimed below. The description above illustrates only a relative few specific embodiments and examples of the present disclosure. The present disclosure, indeed, does include various modifications and variations made to the structures and operations described herein, which still fall within the scope of the present disclosure as defined in the following claims. 

What is claimed is:
 1. A fusion carbide of a refractory metal cementing, comprising: at least four strengthening compound phases and at least one refractory metal cementing phase, wherein the strengthening compound phases and the refractory metal cementing phase are combined by a fusion method, for manufacturing a refractory metal cementing fusion carbide.
 2. The fusion carbide of the refractory metal cementing as claim 1, wherein the strengthening phase compounds are chosen from a group consisting of TiC, ZrC, NbC, VC, TaC, WC, HfC, TiN, and ZrN, for being combined with the refractory metal cementing phase.
 3. The fusion carbide of the refractory metal cementing as claim 1, wherein the refractory metal cementing phase is chosen from a group consisting of Mo, W, Nb, Hf, Ta, and Re, for being combined with the strengthening phase compounds.
 4. The fusion carbide of the refractory metal cementing as claim 2, wherein the fusion method is a vacuum arc melting method executed by the temperature which exceeds 3,500 degrees Celsius, for making the manufactured refractory metal cementing fusion carbide to have a composite structure including a dendrite and an inter-dendrite.
 5. The fusion carbide of the refractory metal cementing as claim 3, wherein the fusion method is a vacuum arc melting method executed by the temperature which exceeds 3,500 degrees Celsius, for making the manufactured refractory metal cementing fusion carbide to have a composite structure including a dendrite and an inter-dendrite. 